Automatic firearm



Oct. 15,1946.A M. M. JoHNsoN, .1R 2,409,569

n AUTOMATIC FIREARM i Filed May 15, 1943 2 sheets-sheet 1 Oct; 15, 1946. M, M, JOHNSON, JR l 2,409,569

AUTOMATIC FIREARM Filed May 13, 1943 2 sheets-sheet 2 v jnamfa fyi .Jam/ w1 Patented Oct. l5, `1946 AUTMATKC FIRE-ARM Melvin M. Johnson, r., Brookline, Mass., a-ssignoi` to Melvin M. Johnson and said` Johnson, Jr.,

both of Brookline, and Edward E. Rice, Boston, Mass., as trustees of Johnson Patent Trust,

Boston, Mass.

Application May 13, 1943, Serial No. 486,782

4 Claims.

This invention relates to automatic guns of the type yhaving a breech closure provided with one or more locking lugs engageable in front of abutments on the receiver to transmit the breech pressure to the receiver, the lugs being movable from their locking positions in front of the abutments `to permit the breech action to recoil, together with a, slide for controlling the movement of the lugs, the slide being movable in unlocking direction in response to the discharge of the iirearm, and a spring for moving the slide in locking direction. While the slide may be actuated by a recoiling barrel vor an inertia member, itis usually gas-operated by tapping gas from the bar-rel in advance of the firing chamber. Whi-le the aforesaid locking lugs may be on a separate locking piece movable transversely of the bolt, 'usually they are fast to the bolt and are moved into and out of locking position by rotating the bolt through an angle ofthe order of to 30 or less. Ordinarily the abutting surfaces between the bolt lugs and the receiver abutments are disposed in a plane or planes perpendicular to the axis of the bolt. Consequently these Vsurfaces freeze tightly together while subjected to the high breech pressure, particularly in high-power firearms of the military type. Even after the breechpressure has dropped to `the point where it is safe. to unlockthe bolt the aforesaid engaging surfaces cling together and strongly resist the unlocking. movement of the lugs. Thus the work imposed'upon the slide in unlocking and opening the bolt is very high, reduiring very rugged constructed of the slide mech- `an'ism and much power to insure complete functioning under all operating conditions.

Objects of the present invention are to provide a construction in which the work imposed upon the aforesaid slide is greatly reduced, in

which the unlocking and opening 'movement of the bolt is controlled largely if not entirely by the breech pressure acting directly on the bolt through the head of the cartridge case, in which the slide mechanism may be simplified and Vreduced in weight, in which the operation of the firearm can be greatly increased, in which the effect of dust and dirt in the operating mechanism is reduced, in which less effort is lrequired to unlock and retract the bolt by hand, in which v the partsare subjected to less batteringand wear in operation, in which there is less danger to burr and score theengaging surfaces of the locking lugsand `receiver abutments and in which theoperation is smoother and more reliable.

According to this invention the abutting surfaces of lthe aforesaid locking lugs and receiver abutments are inclined to the direction of breech pressure so that the-breech pressure tends to` produce unlocking movement of the lugs, and the slide is provided with an abutment surface which obstructs the unlocking movementk of the lug un- Jtil the slide has moved a predetermined distance from firing position. By thus inclining the engaging surfaces of the lugs and abutments the bolt is automatically unlocked by the direct thrust of the breech pressure as soon as the slide has moved far enough to permit the unlocking movement. By increasing the inclination of the abutting surfaces the unlock-ing component of the breech pressure may be increased as much as desired. Forexample the inclination may be merely suflicient to assist the slide in unlocking and retracting the bolt, or it may be large enough to do all of the-Work of unlocking and retracting the bolt, overcoming the friction of the cartridge case in the ring chamber and the friction and inertia of the bolt; indeed it may be great enough not only to do all Vof this work but also to assist in retracting the slide and compressing the recoil spring. For use in military rifles Yand carbines for example the inclination may be in the neighborhood of r20" to 30 with respect to planes perpendicular to the axis of the bolt. In the preferred embodiment the slide also has a cam surface for camming the locking lugs into locking position near the end lof the movement of the slide towardy firing position.

For the purpose of illustration a typical embodiment of the invention is shown in the accompanying drawings in which Fig. 1 is a right side elevation of the firearm lwith parts broken away;

position;

Fig. 6 is a section on line 6-6 of Fig. 5;

Fig. '7 is a section on line 'l-'I of Fig. 4, showing the parts in firing position;

Fig, 8 is a left side elevation of the .forward end of the bolt; and Y Fig. 9 is a right side elevation-of the forward end of the bolt. y

Except for the improvements hereinafter de- 3 scribed the particular embodiment of the invention chosen for the purpose of illustration is like the U. S. caliber .30 SR M1 Carbine and the U. S. caliber .30 M1 (Garand) semi-automatic rie, now being manufactured for the United States Government. Like all M1 Garand rifles and M1 carbines the firearmV comprises a receiver R, a barrel B', a wood stock W, a wood hand-guard G, a detachable magazine M, a sub-frame K for supporting the trigger mechanism, the sub-frame being detachably connected to the receiver at the front and rearV by means including a pin P at the front (Figs, 3 and 5), a bolt- B reciprocating back and forth in the receiver, an extractor V.F mounted on the forward end of the bolt, a gasoperated slide S for controlling the bolt and a recoil spring E for returning the bolt and slide to firing position after recoil, the recoil spring being enclosed by the right slide portion R of the receiver. Extending longitudinally along opposite Sides of the barrel are grooves I to receive the lips of the forward end of the slide (not shown) to guide the slide in its back and forth movement. As shown at Zwin Fig. 3 the barrel has a sloping recess to facilitate assembly.

On opposite Ysides of its forward end the bolt is provided with two locking lugs 3 and 4 which have surfaces 5 and @which engage abutment surfaces Tl and S on the receiver to lock the bolt in firing position. To unlock the bolt it is rotated in a counter-clockwise direction until the locking lugs 3 and l are out of line with the receiver abutments l 'and S, whereupon the bolt is free to recoil without further rotation. In the closing movement the bolt reciprocates forwardly and then rotates in a clockwise direction to bring the locking lug in front of the abutments. While the bolt is reciprocating back and forth, after it has been unlocked and before it has been locked again, rotation is prevented by longitudinal guide surfaces la, and 8a, (Figs. fl, 5 and 6) on the receiver which engage the sides of the lugs 3 and 4. To control the locking and unlocking movement of the bolt the outer end of the right-hand lug 4 cooperates with a groove in the slide S comprising a lengthwise portion having a surface 9 and a sloping portion having surfaces I l and I2 (Fig. 7).

When the parts are in ring position the upper surface E3 of the outer end ofthe bolt lug 4 underlies the slide surface 9 to prevent the bolt from rotating in a 'counter-clockwise direction from locked position. When the gun isfired the slide S is forced to the rear by the gas pressure in the barrel and after it' is moved a limited distance the sloping part of the Yslide groove comes into alignment with the lug 4 permitting the bo-lt to rotate into unlocked position. Thus during the recoil of the bolt and slide together the lug 4 is in the upper end of the sloping portion 'of the slide groove. VAfter recoil when the slide is moved forwardly by the recoil spring E, the sloping surface Vi l of the slide engages the corresponding surface of the lug d, thereby pushing the bolt toward closed position; and as the bolt approaches closed position the surface II cams the boltV into locked position, the slicleS continuing until the lug 4 is under the surface 9.

According to the present invention the surfaces 5 and VI5 of the lockingA lugs 3 and` 4 are inclined instead of'lbeing parallel to .a plane perpendicular to the axis of the bolt', and the cooperating abutments I and 8 of the receiver are correspondingly inclined, the inclinationbeing such that the breech pressure tends to rotate the bolt toward unlocked position, However unlocking Arotation of the bolt is prevented by the surface Q engaging the upper surface I3 of the lug 4 until the slide S has recoiled a considerable distance, by which time the breech pressure has dropped to a value which, while safe for unlocking, is still suiicient to overcome the friction of the cartridge case in the ring chamber, the friction of the bolt onY the receiver, the inertia of the bo-lt and the force of the recoil spring. Thus the slide S is relieved of all work in connection with unlocking and retracting the bolt, which work is very heavy in previous guns having locking surfaces which lie in planes perpendicular to the axis of the bolt and which therefore stick tightly together in response to the breech pressure. The only work left for the slide is the movement of the bolt from retracted position to forward position and the rotation of the bolt into locked position.

In addition to the aforesaid Work of closing and locking the bolt the slide also performs the function of obstructing rotation of the bolt from locked position until the slide has recoiled far enough to releasethe lug d from the surface 9. With the surfaces E-l and 6--8 inclined enough to perform the work of unlocking and retracting the bolt the upward thrust on the surface 9 of the slide by the lug 4 is considerable. To counteract this thrust the receiver is provided with a flange is overlying the upper part I5 of the slide, the flange having a depending portion I6 outside the part l5 so that the slide is confined not only against upward movement but also against outward movement. The ange Ill is connected with the receiver not only by the inner portion I1 (Fig. 4) but also by a fro-nt wall IS (Figs. 5 and 7). By providing the abutment I4 approximately over the place where the upward thrust is imparted to the slide, the thrust is counteracted more effectively and with less strain onthe slide. 'I'his location for the abutment 4 is also advantageous for the reason that it is not in theway and does not interfere with the normal use of the firearm.

I claim:

l. An automatic firearm Vcomprising a receiver,

Va reciprocating breech bolt having one or more locking lugs engageable in front of abutments on the receiver to transmit the breech pressure to the receiver, the bolt being rotatable to remove the lugs from their locking positions in front of the abutments, the abutting surfaces of said lugs and abutments being inclined to the direction of breech pressure so thatthe breech pressure tends to produce unlocking rotation of the bolt, a slide for controlling the movement of the bolt, the

slide being movable in unlocking direction in response to the discharge of the firearm, and a spring for moving the slide in locking direction, the slide having an abutment surface Which Vobstructs said unlocking rotation of the bolt until the'slidehas moved a predetermined distance from firing position in said unlocking direction, the'slide having a `cam surface for camming the Vlocking lugs out of locking position Aafter the slide has moved said predetermined distance from ring position, and the slide also having a cam surface for camming the locking lugs into locking position near the end of the movement of the slide in said locking direction.

2. An automatic firearm comprising a barrel, a receiver, a reciprocating breech bolt having one or more locking lugs engageable in front of abutments on the `receiver to vtransmit the breech pressure to the receiver, the bolt being rotatable to remove the lugs fromtheir locking positions in front "ofthe abutments, the abuttingvsurfaces of said lugs and abutments being inclined to the direction of breech pressure so that the breech pressure tends to produce unlocking rotation of the bolt, a slide for controlling the movement of the bolt, means for moving the slide in unlocking direction in response to gas pressure in said barrel, and a spring for moving the slide in locking direction, the slide having an abutment surface which obstructs said unlocking rotation of the bolt until the slide has moved a predetermined distance from ring position in said unlocking direction, the slide having a cam surface for camming lthe locking lugs out of locking position after the slide has moved said predetermined distance from iring position, and the slide also having a cam surface for camming the locking lugs into locking position near the end of the move ment of the slide in said locking direction.

3. An automatic firearm comprising a receiver, a reciprocating breech bolt having one or more locking lugs engageable in front of abutments on the receiver to transmit the breech pressure to the receiver, the bolt being rotatable to remove the lugs from their locking positions in front of the abutments, the abutting surfaces of said lugs and abutments being inclined to the direction of breech pressure so that the breech pressure tends to produce unlocking rotation of the bolt, a slide for controlling the movement of the bolt, the slide being movable in unlocking direction in response to the discharge of the firearm, and a spring for moving the slide in locking direction, the slide having an abutment surface which obstructs said unlocking rotation of the bolt until the slide has moved a predetermined distance from ring position in said unlocking direction, the slide having a cam surface for camming the locking lugs out of locking position after the slide has moved said predetermined distance from ring position, and the slide also having a cam surface for camming the locking lugs into locking position near the end of the movement of the slide in said locking direction, said receiver having an abutment on the side of the slide opposite to said surface to counteract the thrust of the bolt on the slide While the bolt is moving through said predetermined distance.

4. An automatic firearm comprising a barrel, a, receiver, a reciprocating breech bolt having one or more locking lugs engageable in front of abutments on the receiver to transmit the breech pressure to the receiver, the bolt being rotatable to remove the lugs from their locking positions in front of the abutments, the abutting surfaces of said lugs and abutments being inclined to the direction of breech pressure so that the breech pressure tends to produce unlocking rotation of the bolt, a slide for controlling the movement of the bolt, means for moving the slide in unlocking direction in response to gas pressure in said barrel, and a spring for moving the slide in locking direction, the slide having an abutment surface which obstructs said unlocking rotation of the bolt until the slide has moved a predetermined distance from ring position in Said unlocking direction, the slide having a cam surface for camming the locking lugs out of locking position after the slide has moved said predetermined distance from firing position, and the slide also having a cam surface for camming the 1ocking lugs into locking position near the end of the movement of the slide in said locking direction, said receiver having an abutment on the side of the slide opposite to said surface to counteract the thrust of the bolt on the slide While the bolt is moving through said predetermined distance.

MELVIN M. JOHNSON, Je. 

